Expose avifDecoderItemExtent as avifExtent, and add avifDecoderNthImageMaxExtent() streaming helper function
diff --git a/include/avif/internal.h b/include/avif/internal.h
index 3aae746..3d0cab5 100644
--- a/include/avif/internal.h
+++ b/include/avif/internal.h
@@ -13,6 +13,7 @@
// Yes, clamp macros are nasty. Do not use them.
#define AVIF_CLAMP(x, low, high) (((x) < (low))) ? (low) : (((high) < (x)) ? (high) : (x))
#define AVIF_MIN(a, b) (((a) < (b)) ? (a) : (b))
+#define AVIF_MAX(a, b) (((a) > (b)) ? (a) : (b))
// Used by stream related things.
#define CHECK(A) \
